Oakland police arrest an Occupy protesters during new clashes in that California city yesterday and today. Photo: REUTERS

OAKLAND, Calif. — Dozens of police maintained a late-night guard around City Hall following daylong protests that resulted in 300 arrests. Occupy Oakland demonstrators broke into the historic building and burned a U.S. flag, as officers earlier fired tear gas to disperse people throwing rocks and tearing down fencing at a convention center.

Saturday’s protests — the most turbulent since Oakland police forcefully dismantled an Occupy encampment in November — came just days after the group said it planned to use a vacant building as a social center and political hub and threatened to try to shut down the port, occupy the airport and take over City Hall.

An exasperated Mayor Jean Quan, who faced heavy criticism for the police action last fall, called on the Occupy movement to “stop using Oakland as its playground.”

“People in the community and people in the Occupy movement have to stop making excuses for this behavior,” Quan said.

Protesters clashed with police throughout the day, at times throwing rocks, bottles and other objects at officers. And police responded by deploying smoke, tear gas and bean bag rounds, City Administrator Deanna Santanta said.

Interim Police Chief Howard Jordan said about 300 arrests were made.

“These demonstrators stated their intention was to provoke officers and engage in illegal activity and that’s exactly what has occurred today,” Santana said.

The group assembled outside City Hall late Saturday morning and marched through the streets, disrupting traffic as they threatened to take over the vacant Henry Kaiser Convention Center.

The protesters walked to the vacant convention center, where some started tearing down perimeter fencing and “destroying construction equipment” shortly before 3 p.m., police said.

Police said they issued a dispersal order and used smoke and tear gas after some protesters pelted them with bottles, rocks, burning flares and other objects.

The number of demonstrators swelled as the day wore on, with afternoon estimates ranging from about 1,000 to 2,000 people.

A majority of the arrests came after police took scores of protesters into custody as they marched through the city’s downtown, with some entering a YMCA building, said Sgt. Jeff Thomason, a police spokesman.

Quan said that at one point, many protesters forced their way into City Hall, where they burned flags, broke an electrical box and damaged several art structures, including a recycled art exhibit created by children.

She blamed the destruction on a small “very radical, violent” splinter group within Occupy Oakland.

“This is not a situation where we had a 1,000 peaceful people and a few violent people. If you look at what’s happening today in terms of destructing property, throwing at and charging the police, it’s almost like they are begging for attention and hoping that the police will make an error.”

Dozens of officers surrounded City Hall, while others swept the inside of the building looking for protesters who had broken into the building, then ran out of the building with American flags before officers arrived.

The protest group issued an email criticizing police, saying “Occupy Oakland’s building occupation, an act of constitutionally protected civil disobedience was disrupted by a brutal police response today.”

Michael Davis, 32, who is originally from Ohio and was in the Occupy movement in Cincinnati, said Saturday was a very hectic day that originally started off calm but escalated when police began using “flash bangs, tear gas, smoke grenades and bean bags.”

“What could’ve been handled differently is the way the Oakland police came at us,” Davis said. “We were peaceful.”

City leaders joined Quan in criticizing the protesters.

“City Hall is closed for the weekend. There is no excuse for behavior we’ve witnessed this evening,” City Council President Larry Reid said during a news briefing Saturday.

Oakland Councilman Ignacio De La Fuente, echoed Reid’s sentiments and said that what was going on amounts to “domestic terrorism.”

The national Occupy Wall Street movement, which denounces corporate excess and economic inequality, began in New York City in the fall but has been largely dormant lately.

Oakland, New York and Los Angeles were among the cities with the largest and most vocal Occupy protests early on. The demonstrations ebbed after those cities used force to move out hundreds of demonstrators who had set up tent cities.

In Oakland, the police department received heavy criticism for using force to break up earlier protests. Quan was among the critics, but on Saturday, she seemed to have changed her tune.

“Our officers have been very measured,” Quan said. “Were there some mistakes made? There may be. I would say the Oakland police and our allies, so far a small percentage of mistakes. “But quite frankly, a majority of protesters who were charging the police were clearly not being peaceful.

Earlier this month, a court-appointed monitor submitted a report to a federal judge that included “serious concerns” about the department’s handling of the Occupy protests.

Jordan said late Saturday that he was in “close contact” with the federal monitor during the protests.

Quan added, “If the demonstrators think that because we are working more closely with the monitor now that we won’t do what we have to do to uphold the law and try keep people safe in this city, they’re wrong.”